A user pool set to "MFA: Required" can still let clinicians in on a password alone. This is a practical guide to Cognito MFA for healthcare apps: why federated users bypass enforcement, how the account recovery collision locks people out, why required MFA and adaptive authentication cannot coexist, and how to make session lifetimes match what your documentation claims.
Most accounting-firm document vaults do not fail at the bucket. They fail at the edges: a download link that outlives the engagement, a KMS key policy as wide as the bucket policy, a retention lock that cannot be undone, and an audit trail nobody switched on. Six failure families, and the control that closes each.
Shared admin credentials work right up until someone resigns or an auditor asks who did what. Here's how to design client AWS account access around cross-account roles, unique external IDs and per-engineer attribution, so twenty accounts need zero shared keys and revocation is one action.